The present invention relates to automatic sheet handling apparatus wherein if a sheet is misfed from one paper supply tray the machine automatically switches to another tray without interrupting the job by requiring the user to remove the jammed sheet. The sheet can then be removed when the job is completed giving the appearance of higher reliability. It has particular application in automatic printing apparatus such as printers, copiers and other devices, wherein plural sheet supply means are required. More specifically, it has particular application in electrostatographic imaging wherein an image is formed on a sheet, typically paper.
In the process of electrostatographic printing, a photoconductive surface is charged to a substantially uniform potential. The photoconductive surface is imagewise exposed to record an electrostatic latent image corresponding to the informational areas of an original document being reproduced. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained within the original document. Thereafter, a developer material is transported into contact with the electrostatic latent image. Toner particles are attracted from the carrier granules of the developer material onto the latent image. The resultant toner powder image is then transferred from the photoconductive surface to a sheet of support material such as paper and permanently affixed thereto.
This process is well known and useful for light lens copying from an original and in printing applications from electronically generated or stored originals.
Such automatic printing apparatus takes many forms and has many different capabilities. It may have the capacity, for example, to produce less than 5 prints per minute and over 100 prints per minute. It is common practice to have more than one supply of sheets for such a printing apparatus in order to provide prints on stock of varying sizes and types. It is also not uncommon to have more than one sheet supply tray, for example, be supplied with the same size and kind of sheet to provide increased productivity in long printing runs. It is not unusual even in the smaller, lower volume copiers to have the same size and type of paper in all the paper trays. This increases the amount of paper in the machine and gives it the capacity of a high capacity feeder and versatility of also being able to feed different size paper on demand.
One of the most frustrating events for a customer making prints is to have a copier or printer shut down due to paper jams at the feeder and/or post feeder paper transport. The process of having to clear jams and in some machines the entire paper path along with following instructions for job recovery routines including those of the input device can be very annoying. Furthermore, many customers feel uncomfortable with job recovery routines and many times will clear the jam and rerun the entire job completely from the start. The customer perceives this as a machine unreliability issue which can create a situation of great customer dissatisfaction.